Cryptology ePrint Archive: Report 2006/113

Abstract: In this paper we introduce a new approach of constructing time
capsule signature. Our new construction captures the basic
requirements defined by dodis \emph{et al.}, and it is also very
straightforward and flexible. The time capsule signature provides an
elegant way to produce a ``future signature" that becomes valid from
a specific future time $t$, when a trusted third party (called
\textit{Time Server}) publishes some trapdoor information associated
with the time $t$. It also has many other advantages. Our work
includes a developed security model of time capsule signature, a
novel way of construction based on the bipartite ring signature,
which is proven secure in the random oracle model and a concrete
realization of the scheme.